The role of organoclays in hydrocarbon removal during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The clays used ...for this study were Na-montmorillonite and saponite. These two clays were treated with didecyldimethylammonium bromide to produce organoclays which were used in this study. The study indicated that clays with high cation exchange capacity (CEC) such as Na-montmorillonite produced an organomontmorillonite that was inhibitory to biodegradation of the crude oil hydrocarbons. Extensive hydrophobic interaction between the organic phase of the organoclay and the crude oil hydrocarbons is suggested to render the hydrocarbons unavailable for biodegradation. However, untreated Na-montmorillonite was stimulatory to biodegradation of the hydrocarbons and is believed to have done so because of its high surface area for the accumulation of microbes and nutrients making it easy for the microbes to access the nutrients. This study indicates that unlike unmodified montmorillonites, organomontmorillonite may not serve any useful purpose in the bioremediation of crude oil spill sites where hydrocarbon removal by biodegradation is desired within a rapid time period.
•Organomontmorillonite is inhibitory to biodegradation of crude oil hydrocarbons.•Unmodified montmorillonite stimulates biodegradation of crude oil hydrocarbons.•Adsorption of crude oil hydrocarbons during biodegradation is significant.•Unmodified saponite neither inhibits nor enhances biodegradation of hydrocarbons.
Management of urban brownfield land can contribute to significant removal of atmospheric CO2 through the development of soil carbonate minerals. However, the potential magnitude and stability of this ...carbon sink is poorly quantified as previous studies address a limited range of conditions and short durations. Furthermore, the suitability of carbonate-sequestering soils for construction has not been investigated. To address these issues we measured total inorganic carbon, permeability and ground strength in the top 20 cm of soil at 20 brownfield sites in northern England, between 2015 and 2017. Across all sites accumulation occurred at a rate of 1–16 t C ha−1 yr−1, as calcite (CaCO3), corresponding to removal of approximately 4–59 t CO2 ha−1 yr−1, with the highest rate in the first 15 years after demolition. C and O stable isotope analysis of calcite confirms the atmospheric origin of the measured inorganic carbon. Statistical modelling found that pH and the content of fine materials (combined silt and clay content) were the best predictors of the total inorganic carbon content of the samples. Measurement of permeability shows that sites with carbonated soils possess a similar risk of run-off or flooding to sandy soils. Soil strength, measured as in-situ bearing capacity, increased with carbonation. These results demonstrate that the management of urban brownfield land to retain fine material derived from concrete crushing on site following demolition will promote calcite precipitation in soils, and so offers an additional CO2 removal mechanism, with no detrimental effect on drainage and possible improvements in strength. Given the large area of brownfield land that is available for development, the contribution of this process to CO2 removal by urban soils needs to be recognised in CO2 mitigation policies.
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•Soil carbonate in urban brownfield lands contribute to significant removal of CO2.•Study of 20 brownfield lands show removal rate of 4–59 t CO2 ha−1 yr−1.•CO2 sequestration rate is highest in the first 15 years after demolition.•Sites that sequestered CO2 possess a similar risk of flooding to sandy soils.•Substrate strength, measured in-situ, increased with carbonation
Soil holds 75% of the total organic carbon (TOC) stock in terrestrial ecosystems. This comprises ecosystem-derived organic carbon (OC) and black carbon (BC), a recalcitrant product of the incomplete ...combustion of fossil fuels and biomass. Urban topsoils are often enriched in BC from historical emissions of soot and have high TOC concentrations, but the contribution of BC to TOC throughout the urban soil profile, at a regional scale is unknown. We sampled 55 urban soil profiles across the North East of England, a region with a history of coal burning and heavy industry. Through combined elemental and thermogravimetic analyses, we found very large total soil OC stocks (31–65 kg m–2 to 1 m), exceeding typical values reported for UK woodland soils. BC contributed 28–39% of the TOC stocks, up to 23 kg C m–2 to 1 m, and was affected by soil texture. The proportional contribution of the BC-rich fraction to TOC increased with soil depth, and was enriched in topsoil under trees when compared to grassland. Our findings establish the importance of urban ecosystems in storing large amounts of OC in soils and that these soils also capture a large proportion of BC particulates emitted within urban areas.
To limit warming to well below 2°C, most scenario projections rely on greenhouse gas removal technologies (GGRTs); one such GGRT uses soil carbon sequestration (SCS) in agricultural land. In addition ...to their role in mitigating climate change, SCS practices play a role in delivering agroecosystem resilience, climate change adaptability and food security. Environmental heterogeneity and differences in agricultural practices challenge the practical implementation of SCS, and our analysis addresses the associated knowledge gap. Previous assessments have focused on global potentials, but there is a need among policymakers to operationalise SCS. Here, we assess a range of practices already proposed to deliver SCS, and distil these into a subset of specific measures. We provide a multidisciplinary summary of the barriers and potential incentives towards practical implementation of these measures. First, we identify specific practices with potential for both a positive impact on SCS at farm level and an uptake rate compatible with global impact. These focus on: (a) optimising crop primary productivity (e.g. nutrient optimisation, pH management, irrigation); (b) reducing soil disturbance and managing soil physical properties (e.g. improved rotations, minimum till); (c) minimising deliberate removal of C or lateral transport via erosion processes (e.g. support measures, bare fallow reduction); (d) addition of C produced outside the system (e.g. organic manure amendments, biochar addition); (e) provision of additional C inputs within the cropping system (e.g. agroforestry, cover cropping). We then consider economic and non‐cost barriers and incentives for land managers implementing these measures, along with the potential externalised impacts of implementation. This offers a framework and reference point for holistic assessment of the impacts of SCS. Finally, we summarise and discuss the ability of extant scientific approaches to quantify the technical potential and externalities of SCS measures, and the barriers and incentives to their implementation in global agricultural systems.
To limit warming to well below 2°C, many scenario projections rely on greenhouse gas removal by soil carbon sequestration (SCS) in agricultural land. Here, we provide a multidisciplinary summary of the barriers and potential incentives towards practical implementation SCS. First, we identify specific practices with potential for both a positive impact on SCS and an uptake rate compatible with global impact. Then, we then consider economic and non‐cost barriers and incentives for implementing SCS, and potential externalised impacts of implementation. Finally, we discuss the ability of existing methods to model the potential of SCS in global agricultural systems.
The use of crushed basic igneous rock and crushed concrete for enhanced rock weathering and to facilitate pedogenic carbonate precipitation provides a promising method of carbon sequestration. ...However, many of the controls on precipitation and subsequent effects on soil properties remain poorly understood. In this study, engineered soil plots, with different ratios of concrete or dolerite combined with sand, have been used to investigate relationships between sequestered inorganic carbon and geotechnical properties, over a two-year period. Cone penetration tests with porewater pressure measurements (CPTu) were conducted to determine changes in tip resistance and pore pressure. C and O isotope analysis was carried out to confirm the pedogenic origin of carbonate minerals. TIC analysis shows greater precipitation of pedogenic carbonate in plots containing concrete than those with dolerite, with the highest sequestration values of plots containing each material being equivalent to 33.7 t C ha−1 yr−1 and 17.5 t C ha−1 yr−1, respectively, calculated from extrapolation of results derived from the TIC analysis. TIC content showed reduction or remained unchanged for the top 0.1 m of soil; at a depth of 0.2 m however, for dolerite plots, a pattern of seasonal accumulation and loss of TIC emerged. CPTu tip resistance measurements showed that the presence of carbonates had no observable effect on penetration resistance, and in the case of porewater pressure measurements, carbonate precipitation does not change the permeability of the substrate, and so does not affect drainage. The results of this study indicate that both the addition of dolerite and concrete serve to enhance CO2 removal in soils, that soil temperature appears to be a control on TIC precipitation, and that mineral carbonation in constructed soils does not lead to reduced drainage or an increased risk of flooding.
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•This study presents results from the first large scale inorganic carbon capture experiment in the world.•Our research shows precipitation of 33.7 and 17.5 t C ha−1 yr−1 for plots containing concrete and dolerite, respectively.•At a depth of 0.2 m for dolerite plots, a pattern of seasonal accumulation and loss of carbonate is observed.•Geotechnical measurements shows that carbonation has no observable impact on penetration resistance.•Soil pore water analysis shows carbonation does not change permeability of the substrate, and hence does not affect drainage.
Ammonia-oxidizing archaea are ubiquitous in marine and terrestrial environments and now thought to be significant contributors to carbon and nitrogen cycling. The isolation of Candidatus ..."Nitrosopumilus maritimus" strain SCM1 provided the opportunity for linking its chemolithotrophic physiology with a genomic inventory of the globally distributed archaea. Here we report the 1,645,259-bp closed genome of strain SCM1, revealing highly copper-dependent systems for ammonia oxidation and electron transport that are distinctly different from known ammonia-oxidizing bacteria. Consistent with in situ isotopic studies of marine archaea, the genome sequence indicates N. maritimus grows autotrophically using a variant of the 3-hydroxypropionate/4-hydroxybutryrate pathway for carbon assimilation, while maintaining limited capacity for assimilation of organic carbon. This unique instance of archaeal biosynthesis of the osmoprotectant ectoine and an unprecedented enrichment of multicopper oxidases, thioredoxin-like proteins, and transcriptional regulators points to an organism responsive to environmental cues and adapted to handling reactive copper and nitrogen species that likely derive from its distinctive biochemistry. The conservation of N. maritimus gene content and organization within marine metagenomes indicates that the unique physiology of these specialized oligophiles may play a significant role in the biogeochemical cycles of carbon and nitrogen.
Mineral resources are fundamental to the growth and development of human society. Extraction of metal ores has risen very slightly as a proportion of all resources, while construction and industrial ...mineral extraction has grown much more rapidly. This reflects growth in GDP, which is much faster than population growth, in turn reflecting improved standards of living, growth in urban housing/infrastructure and growth in the consumer society. Fertilizer minerals in particular are essential resources for production of the food needed by an increasing global population. Nitrogen fertilizer manufacture requires fossil fuels—especially natural gas (methane) as a source of the hydrogen needed for the Haber–Bosch process. Phosphate fertilizers are predominantly manufactured using phosphate rock as a source of phosphoric acid, and there is scope to recover phosphorus from contaminated waters. Potassium fertilizers are produced from evaporite deposits, mainly in the global north. It is difficult for poorer countries with deeply leached soils to access and make efficient use of existing conventional products. Globally, while N and P fertilizer application replaces the nutrient removed by crops and so is in balance, twice as much K is being removed from soils as is being replaced. This leads to the need for innovation in developing novel sources of K, especially to support agricultural production in the global south. Rocks containing K silicate minerals (such as feldspar and nepheline) occur widely as potential sources of K for use in soils where these minerals weather rapidly. Observations of surface corrosion in feldspars taken from soils after 10 years exposure to soil microbial systems demonstrates rates of dissolution 4 orders of magnitude greater than determined in the laboratory. Innovation in use of these minerals depends on an understanding of the role of microbial processes in silicate mineral decomposition.
The soil and vegetation of urban greenspace can potentially contribute to ambitious climate action plans declared by city institutions and councils. To assess how urban greenspace could make a ...contribution to institutional carbon management, we measured soil carbon at 42 sampling locations across three land‐covers and vegetation carbon of 490 trees (67 species), over the city campus of Newcastle University. Soil carbon varied with pH and land‐cover classes (lawned with some free‐standing trees, woodland park, sports fields), and tree cover significantly enhanced soil carbon storage. Soil carbon storage from 0 to 30 cm depth averaged 18.85 kg·m−2, more than double the tree carbon storage (average 7.66 kg·m−2) estimated using biomass empirical equations. According to our scenarios, even if all currently available urban greenspace were converted to woodland, this would offset only 1% of current annual greenhouse gas emissions of Newcastle University or, if implemented more widely, of Newcastle city overall. While urban woodland brings benefits beyond carbon storage, the limit to what can be achieved within cities emphasizes the need for urban–rural partnerships. In exchange for helping cities with carbon abatement, their surrounding rural regions could benefit from carbon offsetting payments to improve their infrastructure provision. Overall, a carbon‐friendly and nature‐based land management strategy should be developed with full consideration of collaborative partnerships between urban and surrounding rural areas, particularly placing a high value on soil and tree carbon.
Cation exchange capacity, surface acidity and specific surface area are surface properties of clay minerals that make them act as catalysts or supports in most biogeochemical processes hence making ...them play important roles in environmental control. However, the role of homoionic clay minerals during the biodegradation of polycyclic aromatic compounds is not well reported. In this study, the effect of interlayer cations of montmorillonites in the removal of some crude oil polycyclic aromatic compounds during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The homoionic montmorillonites were prepared via cation exchange reactions by treating the unmodified montmorillonite with the relevant metallic chloride. The study indicated that potassium-montmorillonite and zinc-montmorillonite did not enhance the biodegradation of the polycyclic aromatic hydrocarbons whereas calcium-montmorillonite, and ferric-montmorillonite enhanced their biodegradation significantly. Adsorption of polycyclic aromatic hydrocarbons was significant during biodegradation with potassium- and zinc-montmorillonite where there was about 45% removal of the polycyclic aromatic compounds by adsorption in the experimental microcosm containing 5:1 ratio (w/w) of clay to oil.
•K- and Zn-montmorillonite were inhibitory to biodegradation of crude oil polycyclic aromatic compounds.•Ca- and Fe-montmorillonite stimulated biodegradation of the crude oil PAHs.•Adsorption of crude oil PAHs was significant with K- and Zn-montmorillonite.•The biodegradation of low molecular weight PAHs was not stimulated by the clays.
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